16 June 2010

Study suggests the war on drugs might really be a war on sex

by Kate Melville

Why is there so much heated argument about whether the use of recreational drugs is morally wrong? A new University of Pennsylvania study suggests that the debate about drugs might really be about sex.

Published in the journal Proceedings of the Royal Society B, the new study compared two competing theories about illicit drugs. Traditional theory holds that drug attitudes stem primarily from people's political ideology, level of religious commitment, and personality; for example, their openness to experience. The new theory, proposed by the researchers and driven by ideas from evolutionary psychology, holds that drug attitudes are really driven by people's reproductive strategies.

When the Penn researchers questioned almost 1,000 people in two subject populations (undergraduate students and Internet users) a clear winner emerged between the competing theories: differences in reproductive strategies are driving individuals' different views on recreational drugs.

Researcher Robert Kurzban said that while many factors predict to some extent whether people are opposed to recreational drugs, the most closely related predictors are people's views on sexual promiscuity. "This provides evidence that views on sex and views on drugs are very closely related," he explained. "If you were to measure people's political ideology, religiosity and personality characteristics, you can predict to some degree how people feel about recreational drugs. But if, instead, you just measure how people feel about casual sex, and ignore the abstract items, the predictions about people's views on drugs in fact become quite a bit better."

Somewhat controversially, the study also concludes that considering morality from the standpoint of strategic reproductive interests is a potentially useful way to understand why humans care about third-party behavior.

According to the researchers' evolutionary model, people develop complex differences in their sexual and reproductive strategies. One key difference that creates strategic conflict arises in people's orientations towards casual sexual activity. The relationships of people following a more committed, monogamous reproductive strategy are put at greater risk when casual sex is prevalent. On the other hand, people pursuing a less committed lifestyle seek to avoid having their choices moralized, forbidden and punished.

The researchers cite previous studies showing that recreational drug usage is often associated with promiscuity. This, they say, implies that attitudes against recreational drugs are part of a larger attempt to advance the cause of committed, monogamous reproductive strategies.

"Condemnation of drug usage might be best understood in the context of strategic dynamics, with individuals influencing moral rules in a way that favors their own competitive reproductive strategies," Kurzban said. "We expect that this relationship between sexual strategy and moral stances will occur in other areas as well, such as attitudes toward prostitution, sexual education or abortion."